A need has arisen to deepen many harbors to enable the harbors to accommodate large ships. In many cases the effort to deepen a channel, for example, necessitates the removal of rock from the bottom. Heretofore, blasting techniques have been utilized. However, blasting techniques are extremely expensive in view of the fact that the Environmental Protection Agency requires that the vibrations from such blasting be monitored at many locations around the blasting site as well as the sound produced thereby be monitored. In addition, the Department of Natural Resources has objected to the use of blasting techniques due to the large amounts of marine life that are killed during such under water blasting operations. Thus, blasting operations are generally performed during limited periods of time during the year when certain species of marine life are not present in the channel or harbor. In many instances, the rock removal operation cannot be accomplished within the limited time frame offered by the Environmental Protection Agency and the Department of Natural Resources. Thus, a different method of removing rock from the bottom of harbors and channels is necessary, particularly a method that can be employed during any period of time throughout the year.
Floating barges having various type of equipment thereon adapted to work on the bottom of a body of water have been known for many years. One type of barge having a crane with an outwardly projecting boom thereon is known, which crane has an elongated torpedo-like tool which is lifted by the crane to an elevated position. This torpedo can weigh in the neighborhood of 30,000 pounds which subjects the boom of the crane to a fairly substantial load. At the time the torpedo-like tool is released for free fall back into the water, the sudden release of a 30,000 pound load subjects the boom to a severe amount of whipping, structural fatigue and possibly even failure of the structural members of the boom construction. Thus, the use of this type of equipment to effect a working of the bottom of a body of water has proven to be highly undesirable, time consuming and lacking in precision.
Another form of barge having vertically elevatable chisel-like members thereon is known. This barge is owned by Volker Stevin Dredging bv located in The Netherlands. This barge contains an opening through the central portion of the main deck and plural vertically elevatable chisel-like tools are elevatably supported therein, each being elevated by means of a separate hoist mechanism. The upright mast mounted on the upper deck of the barge is fixedly mounted to the deck and is incapable of any movement relative to the barge. If, however, the chisel-like tool is to work on a surface segment on the bottom of the body of water which is inclined to the horizontal, the inability of the mast to move relative to the upper surface of the barge will make it impossible for the chisel-like tool to strike the bottom surface of the body of water in a direction perpendicular to the general plane thereof, thus limiting the effective energy of the chisel. In addition, the deflection of the chisel would subject any guide structure provided on the barge to a severe amount of stress at the time of impact.
Accordingly, it is an object of this invention to provide a chisel barge having chisel structure thereon capable of working the bottom of a body of water on which the barge is floatably located.
It is a further object of this invention to provide a chisel barge, as aforesaid, having an upstanding mast mounted thereon from which is supported a chisel-like tool capable of being elevated to a raised position spaced from the bottom of the body of water and additionally capable of free falling to a lowered position to impact and effect a working of the bottom of the body of water.
It is a further object of this invention to provide a chisel barge, as aforesaid, having an upstanding mast mounted thereon which can be adjusted from a vertical plane to allow the chisel tools to impact an inclined rock surface perpendicular to the line of fall.
It is a further object of this invention to provide a chisel barge, as aforesaid, wherein shock absorbing structure is provided for normally maintaining the mast in an upright position and for absorption of any shock load generated by the chisel upon impact with the bottom of the body of water.
It is a further object of this invention to provide a chisel barge, as aforesaid, wherein a cable control device is provided for the cable utilized in elevating the chisel to a raised position above the bottom of the body of water, which cable control device prevents an over rotation of the cable drum and resulting "birdcaging" of cable from the cable drum provided therefor following a free fall and impact of the chisel with the bottom.
It is a further object of this invention to provide a chisel barge, as aforesaid, having a position maintaining control structure thereon which allows the barge operator to maintain the steadiness of the barge in its fixed location on the body of water.
It is a further object of this invention to provide equipment which is both durable and generally maintenance-free in its operation as well as, when service is required, easy to service due to the easy access to the tool-like ends on the chisels.